An enzyme sensor, which can quickly and easily determine a concentration of a component to be determined, generally comprises an enzyme for selectively identifying a specific chemical substance such as a molecule and an ion, and a transducer for measuring quantitative change of a substance or heat which is produced or consumed during an enzyme reaction. The transducer, which employs an electrochemical device such as a gas electrode or an ion selective electrode, is mostly used in the field of a clinical chemical examination and a food industry. According to the requirements of miniaturization and integration of enzyme sensors in various fields, a transducer using a semiconductor device, especially an ionsensitive fieldeffect transistor (ISFET), becomes noteworthy. Further, as described in P 246 and 285 of a special feature of enzyme sensors (p. 245-p. 298) in Protein, Nucleic Acid and Enzyme, Vol 30, No. 4, an enzyme sensor employing as a transducer a thermistor working for a heat-measurement is also proposed.
Most of studies in the field of the enzyme sensors have been involved in an enzyme sensor for determining glucose. The enzyme sensors using the transducer as an electrochemical device, a semiconductor device or a heat-measurement device have been also studied. As the enzyme sensor for determining glucose which employs the electrochemical device, it is proposed that glucose oxidase is adopted as an enzyme. This type of sensor utilizes a reaction system in which glucose is changed to hydrogen peroxide and gluconic lactone with consuming oxygen due to an action of glucose oxidase. The enzyme sensor using this reaction is classified into two types. One is the enzyme sensor detecting amounts of consumed oxygen which is in proportion to the concentration of glucose in a sample, with an oxygen electrode. The other is the enzyme sensor detecting amounts of produced hydrogen peroxide which is also in proportion to the concentration of glucose in a sample, with a hydrogen peroxide electrode. It is also known that an amount of oxygen or hydrogen peroxide is determined using an ISFET. In addition to the above mentioned reaction, another reaction system in which glucose is reacted with adenosine-5'-triphosphate (ATP) due to an action of hexokinase to produce glucose-6-phosphate and adenosine-5'-diphosphate (ADP) is also utilized. The enzyme sensor utilizing this reaction system employs as a transducer a heat-measurement device determining amounts of heat produced during the reaction (see Analytical Chemistry, Vol. 47, No. 6, p. 786 to p. 790).
An enzyme sensor for determining adenosine-5'-triphosphate (ATP) employs glucose oxidase and hexokinase as enzymes (EP-OS 125136 corresponding to Japanese Pat. Publication (unexamined) No. 17347/1985). According to this sensor, the reaction of glucose oxidase and glucose is existent with the reaction of hexokinase and glucose and then a ratio of both reactions is changed depending on an amount of adenosine-5'-triphosphate (ATP). Another enzyme sensor for determining adenosine-5'-triphosphate (ATP) employs adenosine-5'-triphosphate hydrolase (AT Pase) with which adenosine-5'-triphosphate (ATP) is hydrolyzed to produce hydrogen ions (see the Gists of Lectures, p. 604 (1985), the 50th Annual Meeting in spring of the Chemical Society of Japan; the Gists of Lectures F-4, p. 7, the 52th Annual Meeting of Electrochemical Society of Japan). In this sensor, the pH change is measured by an ISFET.
Among the above mentioned sensors, a sensor employing glucose oxidase has a long response time because of the lack of oxygen dissolved in a solution. In a sensor employing an oxygen electrode, hydrogen peroxide is also decomposed during the measurement to oxygen and hydrogen oxide. The decomposed oxygen is also detected by the oxygen electrode to causes a measurement error. In the sensor using a hydrogen peroxide electrode, reductive materials in a sample disturb a correct measurement. In case of the sensor employing hexokinase, hexokinase can be effective not only on glucose but also on mannose and fructose to cause preventing a proper measurement. The sensors mentioned above also have a long response time if they are kept without using for a long time and become poor in detecting ratio. Further, if they are repeatedly used, a decline of determining properties becomes significant. In the sensor using adenosine-5'-triphosphate hydrolase (AT Pase), the activity of adenosine-5'-triphosphate hydrolase (AT Pase) loses in a short time and a detecting range is very small.